Apparatus and method for folding an airbag as well as a folded airbag

ABSTRACT

An apparatus for folding an airbag for a vehicle occupant restraint system comprises a base for the airbag to be folded, a cover for the airbag, and a flexible element that is arranged between the base and the cover and has first and second ends. The first end of the flexible element is held between the base and the cover. The apparatus further comprises a traction means that acts upon the second end of the flexible element, and a pressure generating means with which the airbag can be acted upon with compressed gas. The invention further relates to a method of folding an airbag and making use of such an apparatus. Still further, the invention relates to a folded airbag produced by such a method.

TECHNICAL FIELD

[0001] The invention relates to an apparatus for folding an airbag for avehicle occupant restraint system, to a method of folding such an airbagas well as to a folded airbag.

BACKGROUND OF THE INVENTION

[0002] Airbags that can be changed from a folded state into an unfoldedstate through the activation of a gas generator have meanwhile become acommon feature of vehicle occupant restraint systems. An importantrequirement that such an airbag restraint system must fulfill is thatthe airbag has to be able to unfold completely within a very shortperiod of time. The unfolding method is essentially determined by themanner in which the airbag was previously folded.

[0003] In the past, airbags were generally pleated in an accordion-likemanner, for example, using folding blades. However, it was found thatthe relatively large folds created in this manner hinder the unfoldingof the airbag. Nowadays, airbags are often not folded precisely, butrather simply pushed together, resulting in a chaotic folding pattern.The term “chaotic” means that the actual position of the various wallparts of the airbag cannot be predicted and will differ from one airbagto the next. In comparison to conventional methods that use foldingblades, such a chaotic folding or pushing together method offers theadvantage that it calls for less work for the folding and it results inbetter unfolding.

[0004] The object of the invention is to provide an apparatus as well asa method of folding an airbag in chaotic manner, with apparatus as wellas method involving less effort for the folding.

[0005] This is achieved in an apparatus which comprises a base for theairbag to be folded, a cover for the airbag, and a flexible element thatis arranged between the base and the cover and has first and secondends. The first end of the flexible element is held between the base andthe cover. The apparatus further comprises a traction means that actsupon the second end of the flexible element, and a pressure generatingmeans with which the airbag can be acted upon with compressed gas. Theflexible element is arranged in such a way that it loops around theairbag which is disposed between the base and the cover. By pulling onthe second end of the flexible element, the latter is pulled together,forming a loop that gets tighter and tighter. As a result, the airbag ispushed together from the outside towards the inside until it reaches thedesired, completely folded state. In comparison to other apparatus thatwork with pushing elements or blades, this results in an especiallysimple structure, since no complicated movements are needed to fold theairbag; a simple pulling motion on the second end of the flexibleelement is sufficient.

[0006] Preferably, the base and the cover are arranged so as to have adefined distance from each other, the flexible element being a metalstrip having a width which corresponds to this distance between the baseand the cover. This forms a space that is completely enclosed by themetal strip, the base and the cover, and from which the airbag cannotescape when it is being folded. The metal strip is preferably a springsteel strip that, after being pulled together, recovers its original,expanded form once the second end is released.

[0007] According to the preferred embodiment of the invention, it isprovided that the first end of the flexible element is firmly attachedbetween the base and the cover. This facilitates both the mounting ofthe first end of the flexible element and the guidance of the flexibleelement in the area in which the flexible element is pulled out of theapparatus after it has encircled the airbag. After all, this is wherethe gap has to be as narrow as possible, so as to prevent the airbagfrom getting caught in the gap that is present between the flexibleelement forming the loop and the first end of the flexible element.

[0008] When the first end of the flexible element is affixed in themanner described, the entire airbag, except for the area that isimmediately adjacent to the first end of the flexible element, is movedtowards this first end while the airbag is being folded. For thisreason, it is preferable for the base to be provided with a receptaclefor a holding plate of the airbag and for the receptacle to be designedin the nature of a sliding guide. This ensures that the airbag, in spiteof shifting when it is being pushed together, assumes a folded form inwhich its wall is arranged approximately symmetrically around theairbag's inflation opening, which is normally located in the area of theholding plate.

[0009] According to an alternative embodiment, it can also be providedthat the first end of the flexible element is disposed between the baseand the cover in such a way that it can be translatorily shifted. Withthis configuration, the center of the airbag—that is to say, forexample, the inflation opening that is provided with the holdingplate—remains stationary while all of the wall parts are movedsymmetrically from the outside to the inside towards the inflationopening.

[0010] An adjusting cylinder, for instance, can be used to pull theflexible element out of the area between the base and the cover. Such anadjusting cylinder is a component of simple structure, with which theloop encircling the airbag can be pulled together easily, e.g. in adisplacement-controlled or force-controlled manner. When the loop formedby the flexible element is pulled together in a displacement-controlledmanner, the pushing procedure is only terminated once the airbag hasbeen pushed together to a predefined circumference. When the airbag ispushed together in a force-controlled manner, the pulling together ofthe loop is completed as soon as the wall of the airbag offers apredefined resistance against being pushed together any further.

[0011] According to the preferred embodiment of the invention, thepressure generating means is configured as a fan. This makes it possibleto pressurize the inside of the airbag in a simple manner so that theairbag unfolds between the base and the cover as well as the flexibleelement. In this manner, the airbag can be rendered into a partiallyfolded state in which its height corresponds, for example, to the heightof a receptacle provided to receive the airbag. In other words, theairbag is unfolded by the pressure generating means so as to have ashape in which the airbag has only a fraction of the height incomparison to the completely unfolded state.

[0012] In a preferred arrangement, the flexible element is provided witha large number of small openings and the pressure generating means is inflow connection with an outside surface of the flexible element. In thismanner, an air cushion can be generated between the wall of the airbagand the flexible element. The air cushion reduces the friction betweenthe wall of the airbag and the flexible element so that the flexibleelement entrains the walls not so much in the circumferential directionbut rather acts upon them predominantly from the outside towards theinside.

[0013] In order to achieve the above-mentioned objective, a method offolding an airbag is also provided that comprises the following steps:first of all, the airbag is spread out on the base within an area thatis encircled by the flexible element. Then the cover is placed onto theflexible element. Subsequently, the airbag is acted upon with pressure.As a result, it unfolds between the base, the cover and the flexibleelement. Then the flexible element is pulled together by pulling at itssecond end, as a result of which the airbag is pushed together. As faras the advantages of this method are concerned, reference is made to theexplanations above.

[0014] An airbag that is folded together by the apparatus according tothe invention and by the method according to the invention isdistinguished in that its wall has a large number of chaoticallyarranged individual folding lines, several main folding lines beingpresent that run in a slightly spiral shape around a center. Theindividual folding lines result from the essentially radial pushingtogether of the airbag from the outside towards the inside. The mainfolding lines that run in a spiral shape result from the frictionbetween the flexible element and the walls of the airbag; the individualcontact sites between the flexible element and the wall of the airbagexecute a spiral-shaped motion when the loop formed around the airbag bythe flexible element is pulled together.

[0015] Advantageous embodiments of the invention will be apparent fromthe subordinate claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 is a top view of an apparatus according to the invention ina schematic section along the plane I-I of FIG. 2; and

[0017]FIG. 2 is a side view of the apparatus according to FIG. 1 in aschematic section along the plane II-II of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0018] The apparatus for folding an airbag has a base 10, a lid 12 aswell as a side wall 14. On the base 10, there is arranged an airbag 16that is provided with a holding plate 18 in the area of its inflationopening. The holding plate 18 is installed on a carriage 20 that isarranged in a sliding guide 22 in the base 10.

[0019] Perpendicular to the base 10, there is arranged a flexibleelement 24 that is configured as a spring steel strip here. The springsteel strip 24 has a first end 26 that is affixed in a stationaryposition. The second end 28 of the spring steel strip is connected to atraction means 30 that is designed here as an adjusting cylinder. Thespring steel strip 24, as can be seen in FIG. 1, is arranged in a circleor loop around the airbag 16, the circular shape being obtained in thatthe spring steel strip 24, after it has fully encircled the airbag, isguided past the first end 26 and close to same.

[0020] On the spring steel strip 24, a cover 32 is arranged in such away that a space is formed which is enclosed by the base 10, the springsteel strip 24 and the cover 32 and in which the airbag 16 is located.The cover 32 is held in the lid 12 by a threaded connection as a resultof which its distance from the base 10 can be set in such a way thatthere is only a narrow gap between the spring steel strip 24 and thebase or the lid. This prevents the airbag from being able to escape fromthe space between the spring steel strip, the cover 32 and the base 10.

[0021] The apparatus is also provided with a pressure generating means34 that is configured as a fan here. The fan is flow-connected with theinflation opening of the airbag in the area of the holding plate 18, sothat the inside of the airbag can be filled with compressed gas and theairbag can unfold between the base 10, the spring steel strip 24 and thecover 32. The fan 34 is also connected to the space between the sidewall 14 and the spring steel strip 24.

[0022] The spring steel strip 24 is provided with several small openings36 the function of which will be explained below.

[0023] With the lid 12 and the cover 32 removed, the folded airbag isplaced into the space encircled by the spring steel strip 24, the airbagholding plate 18 being connected to the carriage 20. Then the cover 32is mounted together with the lid 12, and the distance from the cover tothe base is set in the desired manner. Then the airbag is pressurized bythe fan 34 so that it unfolds between the cover 32 and the base 10 inthe very flattened shape shown in FIG. 2. The very flattened shape isdistinguished in that the height of the airbag in this state is muchsmaller than the height that it would assume in case of free, completeunfolding.

[0024] By means of the fan 34, the space between the side wall 14 andthe spring steel strip 24 is also pressurized, so that, due to theopenings 36, an air cushion is formed between the outside of the wall ofthe airbag 16 and the spring steel strip 24. Then, by pulling the secondend 28 of the spring steel strip in the direction of the arrow P in FIG.1, the loop formed around the airbag can be pulled together so that theairbag is pushed together radially more and more, until it has finallyassumed the shape shown by the dotted line in FIG. 1. When the airbag isbeing pushed together, the holding plate 18 automatically moves togetherwith the carriage 20 to the left with regard to FIG. 1, since theinflation opening constitutes approximately the middle of the airbag atevery stage of the folding procedure.

[0025] Due to the friction between the walls of the airbag and thespring steel strip 24 being low, the airbag is essentially pushedtogether radially and not so much rotated in the circumferentialdirection. The gap between the first, affixed end 26 of the spring steelstrip 24 and the area of the spring steel strip that is being pulledpast this end is kept as small as possible in order to prevent theairbag from slipping into this gap.

[0026] After the airbag has been completely pushed together, negativepressure can be applied to the inside of the airbag, for example, byreversing the fan 34, so that the airbag is secured in its pushedtogether form and can be placed, for example, into a receptacle or canbe surrounded by a banderole.

1. An apparatus for folding an airbag for a vehicle occupant restraintsystem, said apparatus comprising a base for said airbag to be folded, acover for said airbag, a flexible element that is arranged between saidbase and said cover and has first and second ends, said first end ofsaid flexible element being held between said base and said cover, atraction means that acts upon said second end of said flexible element,and a pressure generating means with which said airbag can be acted uponwith compressed gas.
 2. The apparatus according to claim 1, wherein saidbase and said cover are arranged so as to have a defined distance fromeach other, said flexible element being a metal strip having a widthwhich corresponds to said distance between said base and said cover. 3.The apparatus according to claim 1, wherein said first end of saidflexible element is firmly attached between said base and said cover. 4.The apparatus according to claim 3, wherein said base is provided with areceptacle for a holding plate of said airbag and wherein saidreceptacle is designed in the nature of a sliding guide.
 5. Theapparatus according to claim 1, wherein said first end of said flexibleelement is disposed between said base and said cover in such a way thatit can be translatorily shifted.
 6. The apparatus according to claim 1,wherein said traction means is an adjusting cylinder.
 7. The apparatusaccording to claim 1, wherein said traction means is a cable winch. 8.The apparatus according to claim 1, wherein said flexible element isprovided with a large number of small openings and wherein said pressuregenerating means is in flow connection with an outside surface of saidflexible element.
 9. The apparatus according to claim 1, wherein saidpressure generating means is a fan.
 10. A method of folding an airbag,in particular by means of an apparatus comprising a base for said airbagto be folded, a cover for said airbag, a flexible element that isarranged between said base and said cover and has first and second ends,said first end of said flexible element being held between said base andsaid cover, a traction means that acts upon said second end of saidflexible element, and a pressure generating means with which said airbagcan be acted upon with compressed gas, said method comprising thefollowing steps: said airbag is spread out on said base within an areathat is encircled by said flexible element, said cover is placed ontosaid flexible element, said airbag is acted upon with pressure, saidflexible element is pulled together by pulling at its second end, as aresult of which said airbag is pushed together.
 11. The method accordingto claim 10, wherein said first end of said flexible element is affixedin a stationary position.
 12. The method according to claim 10, whereinsaid first end of said flexible element is translatorily shifted. 13.The method according to claim 10, wherein a negative pressure is appliedto said airbag after it has been pushed together.
 14. The methodaccording to claim 10, wherein said flexible element is pulled togetherin a force-controlled manner.
 15. The method according to claim 10,wherein said flexible element is pulled together in adisplacement-controlled manner.
 16. A folded airbag, in particularfolded by means of a method comprising the following steps: said airbagis spread out on a base within an area that is encircled by a flexibleelement, a cover is placed onto said flexible element, said airbag isacted upon with pressure, said flexible element is pulled together bypulling at a second end thereof, as a result of which said airbag ispushed together, said airbag having a wall which comprises a largenumber of chaotically arranged individual folding lines, several mainfolding lines being present that run in a slightly spiral shape around acenter.